The Timanide, Caledonide and Uralide orogens in the Eurasian high Arctic, and relationships to the palaeo-continents Laurentia, Baltica and Siberia

Abstract

abstract Recent studies of structure, stratigraphy and isotope geochronology on Svalbard and East Greenland have provided a foundation for reconstructing the Laurentian margin of the Arctic segment of the North Atlantic Caledonides. The axial zone of the high Arctic, Barentsian Caledonides has been inferred to trend northwards through the Barents Shelf to the northern edge of the Eurasian margin between Kvitøya (easternmost Svalbard) and western Franz Josef Land, based on analysis of drill-cores that sampled the pre-Carboniferous basement beneath Alexandra Island. The deformation front of the Barentsian Caledonides has been inferred to trend northeastwards between Franz Josef Land and Novaya Zemlya. The North Kara Terrane, reaching from Severnaya Zemlya (SZ) and northernmost Taimyr in the east to northern Novaya Zemlya in the west, comprises the northernmost foreland to the Barentsian orogen. Four lines of independent evidence are presented here demonstrating that the North Kara Terrane is a direct northerly continuation of the Timanide domain, the latter composing the Neoproterozoic accreted margin of Baltica in the Timan-Pechora-Urals region. These lines of evidence, all from October Revolution Island (SZ), include: (1) a westerly source for Old Red Sandstones successions, with 'Caledonian' fish fauna and detrital muscovites yielding Ar/Ar ages of c. 450 Ma; (2) Ordovician igneous rocks containing c. 550 Ma xenocrysts; (3) Cambrian turbidites with c. 545 Ma detrital muscovites; (4) Cambro-Silurian fauna with many species shared with Baltica. In addition, the Neoproterozoic turbidites of northern Taimyr have been previously reported to contain c. 560 Ma zircon populations, a signature that has been recently found in similar lithologies from Bol'shevik Island (SZ). All these late Vendian ages are characteristic of the Timanide Orogen of the Timan-Pechora-Novaya Zemlya region and, together, indicate that the North Kara Terrane was not an independent 'plate' or 'microcontinent' in the Palaeozoic, as previously proposed, but an essential part of southernmost (Ordovician coordinates) Baltica. Comparability of the evolution of the Timanian margin of the North Kara Terrane with the contemporaneous Baikalian evolution of adjacent Taimyr, together with the lack of evidence of Palaeozoic oceanic rocks and Uralian collisional, high-pressure metamorphic assemblages in Taimyr, suggests that the palaeocontinents Siberia and Baltica were never separated by a major ocean in the high Arctic.